High-bandwidth underwater data communication system

ABSTRACT

An apparatus is described which uses directly modulated InGaN Light-Emitting Diodes (LEDs) or InGaN lasers as the transmitters for an underwater data-communication device. The receiver uses automatic gain control to facilitate performance of the apparatus over a wide-range of distances and water turbidities.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §120 asa continuation of U.S. patent application Ser. No. 14/203,550, filedMar. 10, 2014, which claims the benefit of priority under 35 U.S.C. §120as a continuation in-part of U.S. patent application Ser. No.13/843,942, filed Mar. 15, 2013, each of which are hereby incorporatedby reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to the transmission of data between underwaterentities, particular at high data rates.

BACKGROUND

This Background section is provided for informational purposes only, andshould not be considered as an admission that any of the materialcontained in this section qualifies as prior art to the presentapplication.

There is a need for conveying data between two separate underwaterentities in applications including defense, oceanography, hydrocarbondevelopment, etc. Conventional methods for conveying data betweenunderwater entities employ either a tethered link using copper or fiberoptics, or rely on acoustic transmission. According to the formerapproach, the underwater entities must be repositioned or replaced insitu, while the latter approach has a very low data rate (1 to 20kilobits per second is typical) that is currently possible usingacoustic transmission. An approach that uses light propagating freely inthe ocean environment would provide much higher data rates and thepossibility of conveniently exchanging data between arbitrary pairs oftransmitting and receiving devices (transceivers).

Some attempts to implement data transmission between underwater entitiesusing optical means have been frustrated by a lack of suitable lightsources. The propagation of light through water is limited by thefundamental absorption properties of pure water, scattering ofparticulates such as plankton and inorganic particulates, and absorptionby chlorophyl-containing phytoplankton and other organic materials. Thecomponents combine, in various combinations, to favor strongly thetransmission of light in the blue-green region of the optical spectrum,approximately from 400 to 600 nm. The optical effect of the variouscombinations of the components admixed in water can be summarized aswater types and range from the very purest natural waters, which favordeep blue propagation (nominally 450 nm), to waters which favorblue-green (nominally 490 nm) and green (nominally 530 nm) propagation.The minimum optical attenuation coefficients at the optimal wavelengthsvary from about 0.02 m−1 for the very clearest natural waters, to morethan 2 m−1 in the most turbid coastal or harbor waters.

Previous light sources in the blue-green wavelength range have includedbeen bulky, inefficient, expensive and employed external modulators.

SUMMARY

At least one aspect is directed to a method of performing seismicexploration in an aqueous medium. In some embodiments, the methodincludes receiving sub-aqueous environmental data of a first oceanbottom seismometer (OBS) unit. The first OBS unit can be disposed in theaqueous medium. The method can include a data conversion module of theOBS unit converting the sub-aqueous environmental data into an opticalsignal having a first format. The first format can be configured foroptical transmission in the aqueous medium. The method can include anoptical transmitter of the OBS unit transmitting the optical signal inthe first format through the aqueous medium. The method can include anoptical receiver of at least one of a remotely operated vehicle (ROV)and an autonomous underwater vehicle (AUV) receiving the optical signaltransmitted through the aqueous medium. The method can include the atleast one of the ROV and the AUV converting the optical signaltransmitted through the aqueous medium into a non-optical signal havinga second format. The method can include the at least one of the ROV andthe AUV transmitting the non-optical signal in the second format amarine vessel.

In some embodiments, the method can include converting the opticalsignal into the non-optical signal configured for wired transmission toa marine vessel. The method can include transmitting the non-opticalsignal to the marine vessel via a cable. In some embodiments, theoptical receiver can include a first optical transceiver, and theoptical transmitter can include a second optical transceiver. In someembodiments, the non-optical signal transmitted from the at least one ofthe ROV and the AUV to the marine vessel includes an electrical signal.

In some embodiments, the OBS unit is a first OBS unit, the opticalsignal is a first optical signal, and the geophone is a first geophone.In these embodiments, the method can include a second OBS unittransmitting a second optical signal to the first OBS unit through theaqueous medium. The second optical signal can be based on sub-aqueousenvironmental data received via the second OBS unit. The method caninclude the first OBS unit receiving the second optical signal fortransmission to the at least one of the ROV and the AUV.

In some embodiments, the method includes at least one of the OBS unit,the ROV and the AUV determining a characteristic of the aqueous medium.The method can include adjusting a parameter associated with the opticalsignal based on the characteristic of the aqueous medium. In someembodiments, the characteristic comprises at least one of a turbiditymetric, a water quality, a water current, and an opacity. In someembodiments, the parameter includes at least one of a data rate of theoptical signal, an output intensity of the optical signal, a wavelengthof the optical signal, and a gain of the receiver.

In some embodiments, the method includes initiating an optical linkbetween the OBS unit and the at least one of the ROV and the AUV. Themethod can include the OBS unit transmitting a first optical signal tothe at least one of the ROV and the AUV. The first optical signal canhave a first data rate. The method can include determining that a biterror rate of the first signal satisfies a threshold. The method caninclude the OBS unit transmitting a second optical signal to the atleast one of the ROV and the AUV. The second optical signal can have asecond rate that is greater than the first rate, and the second rate canbe transmitted responsive to determining that the bit error ratesatisfies the threshold.

In some embodiments, the method includes initiating an optical linkbetween the OBS unit and the at least one of the ROV and AUV. The methodcan include the OBS unit transmitting a first optical signal having afirst data rate to the at least one of the ROV and the AUV. The methodcan include determining that a bit error rate of the first signal doesnot satisfy a threshold. The method can include selecting a second datarate that is less than the first data rate. The second data rate can beselected responsive to determining that the bit error rate does notsatisfy the threshold. The method can include transmitting a secondoptical signal having the second data rate.

In some embodiments, the method includes initiating an optical linkbetween the OBS unit and the at least one of the ROV and AUV. The methodcan include the OBS unit transmitting a first optical signal having afirst data rate to the at least one of the ROV and the AUV. The methodcan include determining that a bit error rate of the first signal doesnot satisfy a threshold. The method can include adjusting an automaticgain control. The automatic gain control can be adjusted responsive todetermining that the bit error rate does not satisfy the threshold,

In some embodiments, the method can include the OBS unit transmittingthe optical signal via at least one of a solid state light source, anInGaN based light source, a laser, and an LED. In some embodiments, themethod can include the OBS unit transmitting data via the optical signalat a data rate of at least 300 Mbps. In some embodiments, the method caninclude the OBS unit transmitting the optical signal using a channelcoding technique. The channel coding technique can include at least oneof an on-off keyed format, 8 b/10 b encoding, pulse-positiondiscrimination, Quadrature Phase Shift Keying (QPSK), and QuadratureAmplitude Discrimination. In some embodiments, the method can includethe OBS unit transmitting the optical signal using a multi-carriertransmission discrimination technique based on Orthogonal FrequencyDivision Multiplexing (OFDM).

In some embodiments, the sub-aqueous environmental data includes dataindicating at least one of seismic activity, dissolved solids in theaqueous medium, dissolved minerals in the aqueous medium, a state of theaqueous medium, oxygen concentration in the aqueous medium, saltconcentration in the aqueous medium, plankton concentration in theaqueous medium, turbidity of the aqueous medium, and animal presence inthe aqueous medium.

In some embodiments, the sub-aqueous environmental includes seismicdata, and the method includes receiving the seismic data using ageophone of a first ocean bottom seismometer (OBS) unit disposed in theaqueous medium.

In some embodiments, the OBS unit is a first OBS unit, and the methodincludes receiving, by an optical receiver of a second OBS unit, fromthe first OBS unit, the optical signal. The method can include anoptical transmitter of the second OBS unit transmitting the opticalsignal to at least one of the ROV and the AUV. In some embodiments, thesub-aqueous environmental includes seismic data, and the method includesreceiving the seismic data using an accelerometer disposed in the OBSunit.

At least one aspect is directed to a system to perform seismicexploration in an aqueous medium. In some embodiments, the system caninclude a first ocean bottom seismometer (OBS) unit disposed in theaqueous medium. The first OBS unit can be configured to receivesub-aqueous environmental data. The system can include a first dataconversion module of the OBS unit. The first data conversion module canbe configured to convert the sub-aqueous environmental data into anoptical signal having a first format. The first format can be configuredfor optical transmission in the aqueous medium. In some embodiments, thesystem can include an optical transmitter of the OBS unit. The opticaltransmitter can be configured to transmit the optical signal in thefirst format through the aqueous medium. In some embodiments, the systemcan include an optical receiver of at least one of a remotely operatedvehicle (ROV) and an autonomous underwater vehicle (AUV). The opticalreceiver can be configured to receive the optical signal transmittedthrough the aqueous medium. The system can include a second dataconversion module of the at least one of the ROV and the AUV. The seconddata conversion module can be configured to convert the optical signaltransmitted through the aqueous medium into a non-optical signal havinga second format. The system can include a transmitter of the at leastone of the ROV and the AUV. The transmitter can be configured totransmit the non-optical signal in the second format from the at leastone of the ROV and the AUV to a marine vessel.

At least one aspect of the present disclosure is directed to a devicefor transmitting and receiving data optically through an aqueous medium.In some embodiments, the device includes an optical transmitter. Thedevice can also include an optical receiver. The transmitter andreceiver can operate using light with wavelengths in the range of 400nm-600 nm.

In one embodiment, the optical transmitter and optical receiver of thedevice are enclosed in a waterproof container. The optical container caninclude one or more optical windows. Light can be transmitted throughthe one or more optical windows through the waterproof container andinto or out of the aqueous medium.

In one embodiment, the optical transmitter includes at least one solidstate light source.

In one embodiment, the light source is an InGaN based light source.

In one embodiment, the light source includes an LED.

In one embodiment, the light source includes a laser.

In one embodiment, the device is configured to transmit data at a rateof about 10 Mbps or greater.

In one embodiment, the device is configured to transmit data at a rateof about 100 Mbps or greater.

In one embodiment, the device includes a controller configured tomodulate the output of the light source. The controller can modulate theoutput of the light source by varying a drive current to the source.

In one embodiment, the optical receiver includes a photodiode.

In one embodiment, the optical receiver includes at least one from thelist consisting of: a silicon photodiode, silicon PIN photodiode, andavalanche photodiode, and a hybrid photodiode.

In one embodiment, the optical receiver includes a photomultiplier tube.

In one embodiment, the optical receiver includes a micro-channel plateconfigured to detect particles such as photons.

In one embodiment, the photomultiplier tube includes a plurality of gainstages. An output can be extracted from a gain stage prior to a finalgain stage.

In one embodiment, the optical receiver is configured to use ameasurement of the optical signal strength to control the gain of anamplifier following the optical detector.

In one embodiment, the optical receiver is configured to use ameasurement of the optical signal strength to control a gain of theoptical detector.

In one embodiment, the device includes at least one controlleroperatively coupled to one or both of the transmitter and receiver. Thecontroller can be configured to implement a channel coding techniqueduring transmission.

In one embodiment, the device includes at least one controlleroperatively coupled to one or both of the transmitter and receiver. Thecontroller can be configured to dynamically adjust one or moretransmission parameters. The controller can dynamically adjust thetransmission parameters responsive to one or more detected transmissionconditions.

In one embodiment, dynamically adjusting one or more transmissionparameters includes controlling the gain of one or more amplifierelements in the device.

In one embodiment, the device includes at least one controlleroperatively coupled to one or both of the transmitter and receiver. Thecontroller can be configured to implement multi-carrier transmissiondiscrimination techniques.

In one embodiment, the discrimination technique can include opticallybased Orthogonal Frequency Division Multiplexing (OFDM).

In one embodiment, the transceiver is configured to enter a power upstate in response to the detected presence of another data transmissiondevice.

In one embodiment, the device includes a controller configured to aligna local transceiver with a remote transceiver. The controller can alignthe local transceiver with the remote transceiver based on a signal fromthe one or more optical detectors that can sense the relative angle ofthe remote transceiver.

In one embodiment, the device includes a controller configured to aligna local transceiver with a remote transceiver based on a signal from oneor more sensors used to detect the relative position of the remotetransceiver.

In one embodiment, the controller is configured to control a platformfor the device based at least in part on the detected positioninformation.

In one embodiment, the device includes a controller configured tocontrol a plurality of transmitting sources to direct light to theremote transceiver. The controller can control the plurality oftransmitting sources based on a signal from one or more opticaldetectors used to sense the relative angle of the remote transceiver.

In one embodiment, the device includes a controller configured to selectan anode in a multiple-anode photomultiplier tube and align a localreceiver's angular field of view with the remote transceiver. Thecontroller can select the anode and align the local receiver's angularfield view based on a signal from one or more optical detectors that areused to sense the relative angle of a remote transceiver.

In one embodiment, the device includes a controller configured toprovide guidance commands to a platform on which the device is mounted.The one or more optical detectors can be used to sense the relativeangle of a remote transceiver.

In one embodiment, the device is incorporated in an all-optical systemfor transmission of seismic data.

In one embodiment, the one or more diffractive optical elements are usedto collect an optical transmission beam.

In one embodiment, the one or more diffractive optical elements are usedto steer an optical transmission beam.

In one embodiment, one or more diffractive optical elements are used toshape an optical transmission beam.

In one embodiment, the device is mounted on or in at least one from thelist consisting of: a remotely operated vehicle, an autonomouslyoperated vehicle, a submarine vessel, and an ocean bottom seismic node.

In one embodiment, the device includes an acoustic communication device.

At least one aspect is directed to a method that includes opticallytransmitting data through an aqueous medium using light with wavelengthsin the range of 400 nm-600 nm.

In one embodiment, the method includes generating the light using atleast one solid state light source.

In one embodiment of the method, the light source includes an LED.

In one embodiment, the light source includes a laser.

In one embodiment, the step of optically transmitting data includestransmitting data at a rate of at least about 10 Mbps.

In one embodiment, the step of optically transmitting data includestransmitting data at a rate of at least 100 Mbps.

In one embodiment, the step of optically transmitting data includesusing one or more channel coding techniques.

In one embodiment, the step of optically transmitting data includesdynamically adjusting one or more transmission parameters. Thetransmission parameters can be dynamically adjusted in response to oneor more detected transmission conditions.

In one embodiment, the step of optically transmitting data includesimplementing a multi-carrier transmission discrimination technique.

In one embodiment, the discrimination technique includes optically basedOrthogonal Frequency Division Multiplexing (OFDM).

In some embodiments, an output optical transmitted signal can betransmitted through a fiber optic to a window. In some embodiments, aplurality of fiber optics can be bundled together and tapered at one end(e.g., at 1 mm diameter at one and 1 cm at a second end) such that anoptical signal can be transmitted through the window.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric schematic view of one embodiment of a seismicoperation in deep water.

FIG. 2 is a block diagram showing operation of an exemplary pair oftransceivers in communication with each other.

FIG. 3 is an illustration of exemplary pairs of transceivers.

FIG. 4 is an illustration of receiver lenses and correspondingcircuitry.

FIGS. 5-9 are block diagrams of exemplary embodiments of transceivers.

FIG. 10 is an illustration of a system to perform seismic exploration inan aqueous environment using optical transmission, in accordance with anembodiment.

FIG. 11 is an illustration of a method of performing seismic explorationin an aqueous environment using optical transmission, in accordance withan embodiment.

FIG. 12 is an illustration of a system for powering an optical systemfor performing seismic exploration in an aqueous environment.

DETAILED DESCRIPTION

Applicants have recognized that optical data transceivers may beprovided that operate in an aqueous medium, such as a marine environmentin which seismic exploration is performed. In some embodiments, thetransceivers operate with high data transfer rates, e.g., greater thanabout 1 megabit per second (Mbps), about 10 Mbps, about 100 Mbps, about300 MBps, or more (e.g., up to or exceeding about 1 Gbps). In someembodiments, systems and methods can use a variable, asymmetric linkwhere a first optical signal has a first data rate and a second opticalsignal has a second data rate different from the first optical signal.

In some embodiments, the devices use light sources, e.g., lasers lightsources or light emitting diode (“LED”) sources, with outputs in theblue-green region of the spectrum, e.g., with wavelengths in the rangeof 400-600 nm or any subrange thereof.

For example, in some embodiments, solid-state light emitters, e.g.,based upon the Indium-Gallium-Nitride (InGaN) semiconductor materialsnow provide a family of light sources in the blue-green spectral regionthat are efficient, compact, long-lived, and can be directly modulated(their optical output power controlled by the amount of electricalcurrent flow in the device). Such devices may operate at wavelengthsthroughout the blue-green region. Because these devices can be directlymodulated, e.g., by modulating a drive current, they can be arranged inarrays for increased output power or for transmission into other spatialdirections such as between platforms with relative movement.

In some embodiments, the receiver portion of the transceiver deviceincludes one or more optical detectors that are sensitive in theblue-green spectral region that may be compact and reliable. Examplesinclude detectors using semiconductor junctions such as PN junctions orPIN junctions (e.g., silicon PIN photodiodes or avalanche photodiodes).For example, in some embodiments, avalanche photodiodes may be usedthat, with the proper electrical bias voltage applied, exhibitelectronic gain, which can be useful in certain implementations.Photomultiplier tubes may also be used in the blue-green, and have theadvantage, like avalanche photodiodes, of voltage-dependent electronicgain, as well as fast temporal response even with large collectingareas.

In some embodiments, the optical detector's active or photosensitivearea places simultaneous constraints on the collecting area of areceiver lens and the angular field over which light intercepted by thereceiver lens actually lands on the detector (the angular field ofview). Under some applications, particularly where one or anotherunderwater platform is maneuvering, the angular field of view possiblewith temporally optimal detectors will be too small to maintain acommunication connection. Also, it may be useful to reduce the angularspread of the transmitter beam in order to increase the interceptedpower on a remote receiver. In this case it may be advantageous to mountthe transmitter and receiver on controllable mounts (e.g., gimbals), orto provide a mechanism (e.g., an electrical or electromechanicalmechanism) for the transmitter output beam and/or the receiver field ofview to follow a remote transmitter and receiver. Guidance commands forthe motion of the transmitter and receiver can be generated using, e.g.,a system of optical detectors or a multi-element detector withappropriate signal processing to interpret varying light levels from theremote transmitter and guide the direction of the transmitter beam andthe receiver field of view.

FIG. 1 is an isometric schematic view of one embodiment of a seismicoperation in deep water facilitated by a first marine vessel 5. Thefirst vessel 5 is positioned on a surface 10 of a water column 15 andincludes a deck 20 which supports operational equipment. At least aportion of the deck 20 includes space for a plurality of sensor deviceracks 90 where seismic sensor devices are stored. The sensor deviceracks 90 may also include data retrieval devices and/or sensorrecharging devices.

The deck 20 also includes one or more cranes 25A, 25B attached theretoto facilitate transfer of at least a portion of the operationalequipment, such as an autonomous underwater vehicle (AUV), autonomouslyoperated vehicle (AOV), an ROV and/or seismic sensor devices, from thedeck 20 to the water column 15. For example, a crane 25A coupled to thedeck 20 is configured to lower and raise an ROV 35A, which transfers andpositions one or more sensor devices 30 (e.g., OBS units) on a seabed55. The ROV 35A is coupled to the first vessel 5 by a tether 46A and anumbilical cable 44A that provides power, communications, and control tothe ROV 35A. A tether management system (TMS) 50A is also coupledbetween the umbilical cable 44A and the tether 46A. Generally, the TMS50A may be utilized as an intermediary, subsurface platform from whichto operate the ROV 35A. For most ROV 35A operations at or near theseabed 55, the TMS 50A can be positioned approximately 50 feet aboveseabed 55 and can pay out tether 46A as needed for ROV 35A to movefreely above seabed 55 in order to position and transfer seismic sensordevices 30 thereon.

A crane 25B is coupled to a stern of the first vessel 5, or otherlocations on the first vessel 5. Each of the cranes 25A, 25B may be anylifting device and/or launch and recovery system (LARS) adapted tooperate in a marine environment. In this embodiment, the crane 25B iscoupled to a seismic sensor transfer device 100 by a cable 70. Thetransfer device 100 may be a drone, a skid structure, a basket, or anydevice capable of housing one or more sensor devices 30 therein. Thetransfer device 100 may be a structure configured as a magazine adaptedto house and transport one or more sensor devices 30. In one embodiment,the transfer device 100 is configured as a sensor device storage rackfor transfer of sensor devices 30 from the first vessel 5 to the ROV35A, and from the ROV 35A to the first vessel 5. The transfer device 100may include an on-board power supply, a motor or gearbox, and/or apropulsion system (all not shown). Alternatively, the transfer device100 may not include any integral power devices and/or not require anyexternal or internal power source. If needed, the cable 70 may providepower and/or control to the transfer device 100. Alternatively, thecable 70 may be an umbilical, a tether, a cord, a wire, a rope, and thelike, that is configured solely for support of the transfer device 100.

The ROV 35A includes a seismic sensor device storage compartment 40 thatis configured to store one or more seismic sensor devices 30 therein fora deployment and/or retrieval operation. The storage compartment 40 maybe a magazine, a rack, or a container configured to store the seismicsensor devices. The storage compartment 40 may also include a movableplatform having the seismic sensor devices thereon, such as a carouselor linear platform configured to support and move the seismic sensordevices 30 therein. In one embodiment, the seismic sensor devices 30 maybe deployed on the seabed 55 and retrieved therefrom by operation of themovable platform. In this embodiment, the ROV 35A may be positioned at apredetermined location above or on the seabed 55 and seismic sensordevices 30 are rolled, conveyed, or otherwise moved out of the storagecompartment 40 at the predetermined location. In another embodiment, theseismic sensor devices 30 may be deployed and retrieved from the storagecompartment 40 by a robotic device 60, such as a robotic arm, an endeffector or a manipulator, disposed on the ROV 35A.

For example, in a deployment operation, a first plurality of seismicsensor devices, comprising one or more sensor devices 30, may be loadedinto the storage compartment 40 while on the first vessel 5 in apre-loading operation. The ROV 35A, having the storage compartmentcoupled thereto, is then lowered to a subsurface position in the watercolumn 15. The ROV 35A utilizes commands from personnel on the firstvessel 5 to operate along a course to transfer the first plurality ofseismic sensor devices 30 from the storage compartment 40 and deploy theindividual sensor devices 30 at selected locations on the seabed 55.Once the storage compartment 40 is depleted of the first plurality ofseismic sensor devices 30, the transfer device 100 is used to ferry asecond plurality of seismic sensor devices 30 as a payload from firstvessel 5 to the ROV 35A.

The transfer device 100 is preloaded with a second plurality of seismicsensor devices 30 while on or adjacent the first vessel 5. When asuitable number of seismic sensor devices 30 are loaded onto thetransfer device 100, the transfer device 100 may be lowered by crane 25Bto a selected depth in the water column 15. The ROV 35A and transferdevice 100 are mated at a subsurface location to allow transfer of thesecond plurality of seismic sensor devices 30 from the transfer device100 to the storage compartment 40. When the transfer device 100 and ROV35A are mated, the second plurality of seismic sensor devices 30contained in the transfer device 100 are transferred to the storagecompartment 40 of the ROV 35A. Once the storage compartment 40 isreloaded, the ROV 35A and transfer device 100 are detached or unmatedand seismic sensor device placement by ROV 35A may resume. In oneembodiment, reloading of the storage compartment 40 is provided whilethe first vessel 5 is in motion. If the transfer device 100 is emptyafter transfer of the second plurality of seismic sensor devices 30, thetransfer device 100 may be raised by the crane 25B to the vessel 5 wherea reloading operation replenishes the transfer device 100 with a thirdplurality of seismic sensor devices 30. The transfer device 100 may thenbe lowered to a selected depth when the storage compartment 40 needs tobe reloaded. This process may repeat as needed until a desired number ofseismic sensor devices 30 have been deployed.

Using the transfer device 100 to reload the ROV 35A at a subsurfacelocation reduces the time required to place the seismic sensor devices30 on the seabed 55, or “planting” time, as the ROV 35A is not raisedand lowered to the surface 10 for seismic sensor device reloading.Further, mechanical stresses placed on equipment utilized to lift andlower the ROV 35A are minimized as the ROV 35A may be operated below thesurface 10 for longer periods. The reduced lifting and lowering of theROV 35A may be particularly advantageous in foul weather and/or roughsea conditions. Thus, the lifetime of equipment may be enhanced as theROV 35A and related equipment are not raised above surface 10, which maycause the ROV 35A and related equipment to be damaged, or pose a risk ofinjury to the vessel personnel.

Likewise, in a retrieval operation, the ROV 35A utilizes commands frompersonnel on the first vessel 5 to retrieve each seismic sensor device30 that was previously placed on seabed 55. The retrieved seismic sensordevices 30 are placed into the storage compartment 40 of the ROV 35A. Inone embodiment, the ROV 35A may be sequentially positioned adjacent eachseismic sensor device 30 on the seabed 55 and the seismic sensor devices30 are rolled, conveyed, or otherwise moved from the seabed 55 to thestorage compartment 40. In another embodiment, the seismic sensordevices 30 may be retrieved from the seabed 55 by a robotic device 60disposed on the ROV 35A.

Once the storage compartment 40 is full or contains a pre-determinednumber of seismic sensor devices 30, the transfer device 100 is loweredto a position below the surface 10 and mated with the ROV 35A. Thetransfer device 100 may be lowered by crane 25B to a selected depth inthe water column 15, and the ROV 35A and transfer device 100 are matedat a subsurface location. Once mated, the retrieved seismic sensordevices 30 contained in the storage compartment 40 are transferred tothe transfer device 100. Once the storage compartment 40 is depleted ofretrieved sensor devices, the ROV 35A and transfer device 100 aredetached and sensor device retrieval by ROV 35A may resume. Thus, thetransfer device 100 can ferry the retrieved seismic sensor devices 30 asa payload to the first vessel 5, allowing the ROV 35A to continuecollection of the seismic sensor devices 30 from the seabed 55. In thismanner, sensor device retrieval time is significantly reduced as the ROV35A is not raised and lowered for sensor device unloading. Further,mechanical stresses placed on equipment related to the ROV 35A areminimized as the ROV 35A may be subsurface for longer periods.

In this embodiment, the first vessel 5 may travel in a first direction75, such as in the +X direction, which may be a compass heading or otherlinear or predetermined direction. The first direction 75 may alsoaccount for and/or include drift caused by wave action, current(s)and/or wind speed and direction. In one embodiment, the plurality ofseismic sensor devices 30 are placed on the seabed 55 in selectedlocations, such as a plurality of rows R_(n) in the X direction (R₁ andR₂ are shown) and/or columns C_(n) in the Y direction (C₁-C₃ are shown),wherein n equals an integer. In one embodiment, the rows R_(n) andcolumns C_(n) define a grid or array, wherein each row R_(n) comprises areceiver line in the width of a sensor array (X direction) and/or eachcolumn C_(n) comprises a receiver line in a length of the sensor array(Y direction), The distance between adjacent sensor devices 30 in therows is shown as distance L_(R) and the distance between adjacent sensordevices 30 in the columns is shown as distance L_(C). While asubstantially square pattern is shown, other patterns may be formed onthe seabed 55. Other patterns include non-linear receiver lines and/ornon-square patterns. The pattern(s) may be pre-determined or result fromother factors, such as topography of the seabed 55. In one embodiment,the distances L_(R) and L_(C) may be substantially equal and may includedimensions between about 60 meters to about 400 meters, or greater. Thedistance between adjacent seismic sensor devices 30 may be predeterminedand/or result from topography of the seabed 55 as described above.

The first vessel 5 is operated at a speed, such as an allowable or safespeed for operation of the first vessel 5 and any equipment being towedby the first vessel 5. The speed may take into account any weatherconditions, such as wind speed and wave action, as well as currents inthe water column 15. The speed of the vessel may also be determined byany operations equipment that is suspended by, attached to, or otherwisebeing towed by the first vessel 5. For example, the speed is typicallylimited by the drag coefficients of components of the ROV 35A, such asthe TMS 50A and umbilical cable 44A, as well as any weather conditionsand/or currents in the water column 15. As the components of the ROV 35Aare subject to drag that is dependent on the depth of the components inthe water column 15, the first vessel speed may operate in a range ofless than about 1 knot. In this embodiment, wherein two receiver lines(rows R₁ and R₂) are being laid, the first vessel includes a first speedof between about 0.2 knots and about 0.6 knots. In other embodiments,the first speed includes an average speed of between about 0.25 knots,which includes intermittent speeds of less than 0.25 knots and speedsgreater than about 1 knot, depending on weather conditions, such as waveaction, wind speeds, and/or currents in the water column 15.

During a seismic survey, one receiver line, such as row R₁ may bedeployed. When the single receiver line is completed a second vessel 80is used to provide a source signal. The second vessel 80 is providedwith a source device 85, which may be a device capable of producingacoustical signals or vibrational signals suitable for obtaining thesurvey data. The source signal propagates to the seabed 55 and a portionof the signal is reflected back to the seismic sensor devices 30. Thesecond vessel 80 may be required to make multiple passes, for example atleast four passes, per a single receiver line (row R₁ in this example).During the time the second vessel 80 is making the passes, the firstvessel 5 continues deployment of a second receiver line. However, thetime involved in making the passes by the second vessel 80 is muchshorter than the deployment time of the second receiver line. Thiscauses a lag time in the seismic survey as the second vessel 80 sitsidle while the first vessel 5 is completing the second receiver line.

In this embodiment, the first vessel 5 utilizes one ROV 35A to laysensor devices to form a first set of two receiver lines (rows R₁ andR₂) in any number of columns, which may produce a length of eachreceiver line of up to and including several miles. In one embodiment,the two receiver lines (rows R₁ and R₂) are substantially parallel. Whena single directional pass of the first vessel 5 is completed and thefirst set (rows R₁, R₂) of seismic sensor devices 30 are laid to apredetermined length, the second vessel 80, provided with the sourcedevice 85, is utilized to provide the source signal. The second vessel80 is typically required to make eight or more passes along the tworeceiver lines to complete the seismic survey of the two rows R₁ and R₂.

While the second vessel 80 is shooting along the two rows R₁ and R₂, thefirst vessel 5 may turn 180 degrees and travel in the −X direction inorder to lay seismic sensor devices 30 in another two rows adjacent therows R₁ and R₂, thereby forming a second set of two receiver lines. Thesecond vessel 80 may then make another series of passes along the secondset of receiver lines while the first vessel 5 turns 180 degrees totravel in the +X direction to lay another set of receiver lines. Theprocess may repeat until a specified area of the seabed 55 has beensurveyed. Thus, the idle time of the second vessel 80 is minimized asthe deployment time for laying receiver lines is cut approximately inhalf by deploying two rows in one pass of the vessel 5.

Although only two rows R₁ and R₂ are shown, the sensor device 30 layoutis not limited to this configuration as the ROV 35A may be adapted tolayout more than two rows of sensor devices in a single directional tow.For example, the ROV 35A may be controlled to lay out between three andsix rows of sensor devices 30, or an even greater number of rows in asingle directional tow. The width of a “one pass” run of the firstvessel 5 to layout the width of the sensor array is typically limited bythe length of the tether 46A and/or the spacing (distance L_(R)) betweensensor devices 30.

Referring to FIG. 2, an optical communication system that transmit datathrough an aqueous medium includes a first optical transceiver 10 and asecond optical transceiver 20. Each optical transceiver includes anoptical transmitter 100 and an optical receiver 200. As shown, theoptical transmitter 100 and an optical receiver 200 of transceiver 10are packaged together in a housing 300 to provide bi-directional datatransmission with a similarly packaged optical transceiver 20.

Each of the transceivers may be mounted on any suitable platformincluding an underwater vehicle (e.g., subsea equipment, a submarine,remotely operated vehicle, or autonomously operated vehicle), anunderwater device (e.g., an ocean bottom seismic node, such as the typesavailable from FairfieldNodal, Inc. of Sugarland, Tex.), an underwaterstructure (e.g., an oil drilling or pumping platform), or any othersuitable object.

A transmitter and receiver packaged together are referred to as atransceiver. Although the embodiments shown focus on transceiverpackages, it is to be understood that in various embodiments, thetransmitter and receiver may be separately packaged. In someembodiments, a single transmitter in a single receiver may be used foruni-directional communication.

As shown in FIG. 2, simultaneous bi-directional data transmission may beaccomplished by the use of spectrally separated wavelengths, so that thetransmitter 1 of transceiver 10 may transmit a wavelength 1 (forexample, a blue wavelength or band of wavelengths, such as might beemitted by an InGaN LED) and the transmitter 2 of transceiver 20transmits a wavelength 2 for example, a blue-green or green wavelengthor band of wavelengths). The receiver 2 of transceiver 20 can receivethe wavelength 1 of transmitter 1 and reject the wavelength 2 oftransmitter 2 and all or as many as possible wavelengths outside theband of wavelength 1 using optical filters. Other data transmissionschemes may be employed as well. For example, instead of separating theupstream and downstream signals by wavelength, they may instead betransmitted using time-division multiplexing or by polarization.Similarly, code-division multiplexing and other data transmissionschemes may be used.

Various embodiments include the capacity to incorporate multi-carriertransmission discrimination techniques such as optically basedOrthogonal Frequency Division Multiplexing (OFDM). Many closely spacedsubcarriers are utilized to increase the overall transmission rate. Theoptical data can also be transmitted using coherent OFDM, CO-OFDM,protocols using single carrier or multicarrier transmission schemes. Insome embodiments, discrimination or discrimination techniques can referto optical discrimination techniques.

Similarly receiver of transceiver 1 may be configured to receivewavelength 2 of transmitter 2 and reject the wavelength of transmitter 1and all or as many as possible wavelengths outside of the band ofwavelength 2.

Another embodiment, shown in FIG. 3, provides for bidirectionaltransmission by spatial separation of the respective transmitters andreceivers. Here the transmitter 1 of transceiver 1 is aligned (e.g.,closely aligned) with receiver 2 of transceiver 2, and the transmitter 2of transceiver 2 is aligned (e.g., closely aligned) with the receiver 1of transceiver 1, so as to prevent light emitted by transmitter 1 butscattered by the intervening aqueous medium from entering receiver 1,and similarly the light from transmitter 2 but scattered by theintervening aqueous medium is unable to enter receiver 2. In someembodiments, the optical transceivers 10 and 20 can include one or morefilters configured to prevent, limit, block, or otherwise filter lightcoming from one or more directions (e.g., to limit off-axis visibility).In a non-limiting example, the one or more filters may include ahoneycomb filter or a directionally selective optical plate. Forexample, in order to discriminate unwanted photon sources, a directionsorting device such as a light control film, window blind louver type orelement or the like may be used.

Various embodiments may include one or more mechanisms to direct theoutput light from a transmitter in the direction of a receiver and/or tocause the field of view of a receiver to track the output of atransmitter. In addition to mechanical scanning of the transmitter andreceiver to change the pointing direction, electronic systems may alsobe used. An electronic system capable of scanning the transmitterdirection may arrange a plurality of individual light sources (e.g. LEDsor lasers), or a plurality of arrays of light sources, pointing indifferent directions so that the device or array pointing in thedirection of interest can be used to transmit the data, as shown in FIG.2. In this way the power consumption of the transceiver can besignificantly reduced compared to a system that transmits power into alarger angular field of view.

For example, FIG. 4 shows an electronic mechanism for scanning thereceiver field of view using a multiple-anode photomultiplier tube 410,in which separate gain-producing dynode arrays and anodes are providedin a one- or two-dimensional arrangement such that light striking aspatial location on the photocathode produces an electrical signal atthe anode corresponding to the photocathode spatial location. By placingthe multiple-anode photomultiplier tube 410 at the focus of a lens 215the angular position of the remote transmitter beam is converted into aspatial location on the photocathode. This receiver can serve a dualpurpose; sensing the location of the remote transmitter for guidance;and by selecting only the anode corresponding to the photocathodelocation where the transmitter signal is detected a specific field ofview can be obtained, as in FIG. 2, thereby rejecting interfering lightsources.

The components of an exemplary optical transceiver are now describedwith reference to FIG. 5. The transmitter 100 comprises a series ofelectronic components used to convert an incoming data signal into anoutgoing optical signal that can be transmitted through the aqueousmedium. A data signal is conducted to a data conversion module 110,which converts the incoming data for transmission via a non-opticaldomain, typically conveyed using either a conducting cable or afiber-optic cable, into an on-off keyed format, such as 8 b/10 bencoding or pulse-position discrimination, which is appropriate for useby the transmitter. This module may typically also provide the functionsof ascertaining whether a data connection is present on the cable side,and in turn provide a signaling format that the transmitter can transmitto a remote receiver so as to alert the remote transceiver as to itspresence. The output of the data conversion module 110 is conveyed to atransmitter drive module 120, which receives the output of the dataconversion module 110 and by use of amplifiers and other electroniccomponents converts the output of the data conversion module 110 into adrive signal for the light source 130, either singly or in a plurality(e.g., an array), such that the optical output of the light source 130varies between a lower optical power state (e.g., with little or nooptical output) and a higher optical power state.

The electronic circuits of the transmitter drive module 120 may bedesigned so as to maintain as much fidelity as possible between thetemporal characteristics (pulse width, risetime and falltime) of theelectronic output waveform of the data conversion module 110 and theoptical output waveform of the light source 130. This may require acombination of electronic feedback within the amplifier circuits,temperature compensation to correct for temperature-induced changes inthe optical output of the light source 130 for a given electricalcurrent conveyed from the transmitter drive module 120, or opticalfeedback from the light source 130 into circuits associated with thetransmitter drive module 120 such that the optical waveform exhibitsmaximum fidelity to the input electrical waveform.

As noted above, the light source may be, for example, an LED source or alaser source, such as an InGaN based LED or current driven solid statelaser such as an InGaN laser. The choice of whether an LED or laser isused will depend largely on the data bandwidth required. In someembodiments, it may be difficult to achieve to achieve data bandwidthsof much greater than 10 or 20 Mbps using LEDs due to carrier-lifetimeeffects in the PN junction leading to long temporal decays of theoptical output.

In contrast, laser sources may operate with a significantly shortertemporal pulse width. In some embodiments this is because when the drivecurrent to the laser drops below a threshold level, lasing ceases, andthe output intensity of the laser rapidly decreases. Similarly, as thedrive current increases across the lasing threshold, the outputintensity of the laser may rapidly increase. Accordingly, the modulatedlaser output may reproduce even a rapidly modulated drive signal withvery high fidelity. Accordingly, in some embodiments, a data ratetransmission rate of greater than 10 Mbps, 50 Mbps, 75 Mbps, 100 Mbps,200 Mbps, 300 Mbps, 400 Mbps, 500 Mbps, 600 Mbps, 1000 Mbps or more maybe provided.

The optical output of the light source may be modified in angular extentby use of an optical element 140. The optical element 140 may be, forexample, a transparent epoxy lens integral to an LED or diode laser inan industry-standard package, or, particularly in the case of a laser inlieu of an LED, this external element may be a lens or other refractive,reflective, or diffractive element as required to shape the transmitterbeam into the desired angular field.

A power supply 170 is provided to condition input power from theplatform hosting the transmitter 100 and provide the required voltagesand currents to power the various electronic modules of the transmitter100. This power supply 170 may typically be a high-efficiency, low-noiseswitching supply, with one or more outputs.

The receiver 200 of the optical transceiver will generally comprise anoptical element 210 which collects incoming light and directs it to thephotosensitive area of an optical detector 230. The optical element 210may be a spherical or aspherical lens, or another reflective,refractive, or diffractive optical element (or grouping of elements)selected so as to match the desired angular field and collecting areawith the photosensitive area of the detector. In one embodiment a fieldlens 215 may be added following the optical element 210 in order toilluminate the surface of the optical detector 230 more uniformly.

An optical filter 220 (or any other suitable wavelength selectiveelements) will either precede the optical element 210 (be placed on theside towards the remote transmitter 100) or follow the optical element210 but precede the optical detector 230. The purpose of the opticalfilter is to as completely as possible transmit only the opticalwavelength or wavelengths corresponding to those emitted by the remotetransmitter 100 and to reject as completely as possible the wavelengthor wavelengths emitted by an adjacent transmitter, as well as ambientsunlight and other extraneous light. The optical filter 220 may include,for example, a color (absorbing) glass filter, a color (absorbing)plastic filter, or an interference (reflecting) filter or wavelengthdiffractive element, as appropriate to the required optical bandwidth,rejection and angular acceptance. In some embodiments, the opticalfilter 220 may include a special filter, a general filter, a customdesigned filter or other type of filter configured to facilitate opticalbandwidth rejection).

The optical detector 230 converts the light collected by optical element210 and transmitted by optical filter 220 into an electrical signal forfurther processing. The optical detector is followed by an amplifiermodule 240. In one embodiment the optical detector 230 may be asemiconductor detector such as a silicon PIN photodiode. In thisembodiment the amplifier module 240 comprises a preamplifier and anautomatic gain control amplifier to amplify the electrical output of thephotodiode to match the electrical output to electronic stages. A powersupply 235 provides a low bias voltage to the PIN photodiode to reduceshunt capacitance and improve temporal response.

In some embodiments, e.g., as illustrated in FIG. 6, using an avalanchephotodiode as the optical detector 230 the power supply 235 would be ofa higher voltage to drive the photodiode into the avalanche regime andprovide electronic gain. In this embodiment the power supply 235 wouldtypically have a temperature sensor (such as a thermistor) to monitorthe avalanche photodiode temperature and automatically adjust thevoltage output to compensate for temperature dependence in the avalanchevoltage of the avalanche photodiode. In this embodiment the amplifiermodule 240 may also provide a small fraction of the amplified electricalsignal to an automatic gain control module 250 which integrates theelectrical signal, conditions it and supplies it to a voltage-controlinput of the power supply 235, thereby controlling the voltage of thepower supply 235 and thereby the gain of the avalanche photodiode tomatch varying light levels received at the optical detector 230 due toreceived transmitter light or other detected light.

The automatic gain control module may itself, e.g., in its own internalcircuits, include variable gain to keep the output signal within therequired range for subsequent processing (such as in the discriminationmodule 260).

In an embodiment using a photomultiplier tube the as the opticaldetector 230 a power supply 235 supplies high voltage (100-500V typical)to the photomultiplier tube in order to provide fast temporal responseand electronic gain. Typically the power supply 235 in this embodimentwill have a voltage control input, as in an embodiment using theavalanche photodiode, so that a similar automatic gain control module250 can control the voltage supplied to the photomultiplier tube andthereby its electronic gain to match varying light levels received atthe optical detector 230 due to received transmitter light or otherdetected light, as well as to protect the photomultiplier tube fromdamage due to high light levels.

In an embodiment that uses a photomultiplier tube at data rates above,e.g., 100 Mbps, such as 622 Mbps or 1000 Mbps, special consideration maybe taken with the choice of photomultiplier tube. A very high bandwidthtube may be required, and particular care may be needed in itsoperation. For example, it may be necessary to utilize only the firstfew stages of a conventional high-speed photomultiplier tube, drawingthe signal current from an intermediate dynode stage, rather than fromthe anode, in order to obtain fast enough rise and fall times to supportthe high bit rate. In an additional embodiment a photomultiplier tubewhich uses a micro-channel plate as the electronic gain medium in lieuof a conventional dynode structure may be used. In a further embodiment,a hybrid photodiode may be used, a device which combines a vacuum stageoperating at high voltage followed by an internal semiconductoravalanche structure may be used to provide a significant photosensitivearea and electronic gain while supporting the bandwidth required for,e.g., 1000 Mbps operation. In another embodiment, a vacuum photodiode,which provides a large collecting area and high speed without internalelectronic gain may be used, provided that sufficient gain can beprovided in subsequent electronic amplification stages.

The output of the amplifier module 240 is conveyed to a discriminationmodule 260 which detects the amplified waveform using a waveformdetection module which may include, e.g., Schmidt triggers, clocks andother circuits to convert the detected waveform into a signal that canbe conveyed to the data conversion module 270 which converts the dataformat created by the discrimination module 260 from the detectedoptical waveform into a non-optical format useable for an external datarecipient located on the host platform.

A power supply 280 is provided to condition input power from theplatform hosting the transmitter 100 and provide the required voltagesand currents to power the various electronic modules of the receiver200. This power supply 280 may typically be a high-efficiency, low-noiseswitching supply, with one or more outputs.

In the case of infrequent data exchanges, a power control module 290,which uses an optical detector and a low-powered circuit with anamplifier, electronic filter, a threshold circuit and a relay orelectronic switch may be provided to sense the proximity of a remotetransmitter and activate the local transmitter and receiver byconnecting the input power between the power supply 170/280 and thepower source on the platform.

In the embodiment illustrated in FIG. 2 the transmitter 100 and thereceiver 200 will be collocated in a pressure vessel 300 in order toisolate the transmitter 100 and receiver 200 from contact with theaqueous environment. In this embodiment windows 310 will be provided toconvey light from the transmitter 100 into the aqueous medium and to aremotely mounted receiver, and from a remotely mounted transmitterthrough the aqueous medium to the receiver 200. These may typically beseparate windows for the transmitter and receiver, but can also be asingle window serving both transmitter and receiver.

In an embodiment in which the directions of the transmitter beam and/orreceiver field of view must be moved during operation (such as forcommunication between a moving and a stationary transceiver) an elementis provided that senses the direction of a remote transmitter andgenerates control signals for a gimbal or other mechanical device thattranslates the pointing angle of the transmitter or receiver, or for anelectronic pointing angles translator. FIG. 6 shows one embodiment,useful for the case where the angular directions must be controlled inone dimension only, in which an array of optical detectors 410 arepointed in different angles to sense the incoming transmitter beam. Theoptical detectors are provided with optical filters 415 (or otherwavelength selective elements) to transmit light from the remotetransmitter and reject backscattered light from the local transmitter.The optical detectors may also be provided with lenses 420 or anotheroptical element capable of defining the optical detector field of view.The electrical signal from the optical detectors 410 is conveyed to anamplifier module 440. The amplifier module 440 will typically includeautomatic gain control in order to maintain the output signal within therange of voltage levels useable by following stages. The electricaloutput from the optical detectors is conveyed to a guidance processormodule 460 which measures the signal strength from each optical detectorand calculates the direction of the remote transmitter. The calculationcan be accomplished for coarse direction by taking the ratios of thestrengths of the optical signals using either a system of operationalamplifiers or by using an actual analog to digital conversion andperforming the calculation in a microprocessor system. A more precisecalculation of the direction of the remote transmitter can beaccomplished in a microprocessor by taking into account the geometry ofthe detectors and the amount of remote transmitter light that will beintercepted by them as a function of angle.

Another embodiment illustrated in FIG. 8 uses a position-sensitiveoptical detector 520 such as a position-sensing semiconductor photodiode(e.g., a split photodiode), position-sensing (e.g., resistive anode)photomultiplier tube, or a multiple-anode photomultiplier tube with avoltage divider circuit to provide the angular location of the remotetransmitter. An imaging optical element 410 such as a lens is used toconvert the angle of the incoming transmitter light into a position onthe active area of the positions-sensitive optical detector 520. Anoptical filter 415 can be used to transmit light from the remotetransmitter and reject ambient background light and backscattered localtransmitter light. The electrical output of the position-sensitivedetector 520 is conveyed to an amplifier module 440 and the output ofthe amplifier module 440 conveyed to a guidance processor module 460 forthe generation of guidance signals. The guidance signals generated fromthis embodiment are accurate enough for precision platform guidance, ifneeded.

In addition to wavelength-selective optical filter 415, in order toreject background light (such as sunlight when the transceivers areshallow) an electronic filter may be included either in the amplifiermodule 440 or in the guidance processor module 460 in order to rejectsteady or slowly varying (un-modulated) optical signals and accept themodulated signal from the remote transmitter.

The output of the guidance processor module 460 is conveyed to a drivemodule 470 which provides electrical signals to a motor driven gimbal480 (or other positioning device) on which are mounted the transmitterand receiver such that an electrical signal from the drive module 470translates the angle of the transmitter and receiver relative to thehousing. A power supply 490 is provided to condition power from theplatform and provide the required voltages and currents to therespective modules.

Another embodiment illustrated in FIG. 9 uses the output of the guidanceprocessor module 460 to select angularly separated transmitter lightsources or light source arrays 610 so as to project a transmitter beaminto the desired direction. Another embodiment uses the output of theguidance processor to switch the output of a multiple-anodephotomultiplier tube used as the optical detector so as to select thedirection for which an incoming light beam will be sensed.

In some embodiments, the transceivers described herein may use channelcoding techniques to increase link robustness and transmission rates.For example, low-density parity-check, LDPC, codes and rate adaptivechannel codes may be used.

In some embodiments, the transceivers described herein may implementdynamic optimization of the transmission parameters. In underwaterenvironments such as seismic sensing, the local water conditions canvary significantly. In order to accommodate the variation the opticallinks are dynamically configured to measure link loss mechanisms, aloneor in combinations with other effects such as dispersion, and assign anoptimal data rate. In addition, if the underwater environmentalconditions permit, multi-carrier modes can be initiated. Local DigitalSignal Processing, DSP, can be performed to adjust or compensate for theapplicable transmission-reception parameters, or software can implementthe communication control adjustments. The optical transmission receiverlinkage can be monitored continuously in order to maintain linkperformance.

In some embodiments, receivers of the type herein may be used totransmit seismic data, e.g., from an autonomous underwater seismic nodeto a retrieval device. The retrieval device may be mounted on, forexample, an submarine vessel, a remotely operated vehicle, or anautonomously operated vehicle. In some embodiments, the seismic datatransfer may be performed at a rate of at least 10 Mbps, 100 Mbps, 500Mbps, 1000 Mbps or more. In some embodiments, the transmission link ismaintained for at least 1 second, 10 seconds, 1 minute, 5 minutes, 10minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 1 hour, ormore. In some embodiments, the transmission occurs over a distance of atleast 10 cm, 100 cm, 1 m, 2 m, 3 m, 5 m, 10 m, 20 m, 100 m or more.

Although in many embodiments (e.g., as described herein) it isadvantageous to used wavelengths in the range of 400-600 nm (or anysubrange thereof), in other cases depending on the application at handany other suitable wavelengths may be used (e.g., wavelengths in therange of 300 nm to 1400 nm).

FIG. 10 is an illustration of a system 1000 to perform seismicexploration in an aqueous environment using optical transmission. Insome embodiments, the system 1000 includes a first optical link 1001that transmits and receives optical signals to/from or between a secondoptical link 1003. In some embodiments, the first optical link 1001 andthe second optical link 1003 can include one or more of the samecomponents. The one or more same components may be configured in acomplimentary manner such that the transmission component of the firstoptical link 1001 is configure to transmit optical signals to areceiving component of the second optical link 1003.

In some embodiments, the first optical link 1001 includes a magneticmodule 1002 configured to isolate voltages in an Ethernet networkconnection. The magnetic module 1002 can isolate voltage so thatequipment operating from different voltage sources can coexist on asingle network. In some embodiments, where one or more components ofsystem 1000 or other network components are powered from the same powersupply, it may not be necessary to include the magnetics module 1002. Insome embodiments, the magnetics module 1002 includes one or moretransformers configured to blocks DC and low frequency voltages. In someembodiments, the magnetics module 1002 is a hardware module that isexternal to the PCB, and not part of the FPGA. In some embodiments, themagnetics module 1002 may be internal to the FPGA or otherwisecommunicatively coupled to the FPGA to facilitate systems and methods ofperforming seismic exploration using optical transmissions.

In some embodiments, the system 1000 includes a phy module or “physicallayer” module 1004. The phy module 1004 may refer to a low layer (e.g.,or a lowest layer) in an Open Systems Interconnection model of anetwork. The phy module 1004 is configured to transmit and receivessignal based on one or more specifications such as Ethernet, WiFi,WiMax, Bluetooth, Near Field Communications, etc. In some embodiments,the phy module includes one or more chips on one or more circuit cardsthat are external the FPGA. In some embodiments, the phy module 1004 maybe internal to the FPGA or otherwise communicatively coupled to the FPGAto facilitate systems and methods of performing seismic explorationusing optical transmissions.

In some embodiments, the system 1000 includes an FPGA 1006 (e.g., afield-programmable gate array having one or more integrated circuitsthat can be configured to facilitate seismic exploration in an aqueousenvironment). In some embodiments, the FPGA 1006 can include one or moreMedia Access Controller (MAC) (e.g., a first MAC 1008 and a second MAC1010). The first and second MACs 1008 and 1010 can represent the secondlayer of the Open Systems Interconnection model. The first and secondMACs 1008 and 1010 can be configured to perform one or more of thefollowing functions: receive/transmit frames, retransmit and backofffunctions, inter-frame gap enforcement, and discard malformed frames. Insome embodiments, the first MAC 1008 (or topside MAC) can transmit andreceive data via an Ethernet connection (e.g., the Phy 1004 andmagnetics 1002), and the second MAC 1010 (or bottomside MAC) cantransmit and receive data via an optical connection.

In some embodiments, the FPGA 1006 includes a micro-processor 1012. Themicro-processor 1012 can be communicatively coupled to the first andsecond MACs 1008 and 1010, respectively. The micro-processor 1012 can beconfigured to receive data frames from a host and buffer the data framesuntil the system is ready for the data frames. The micro-processor 1012may include or have access to memory configured to store the receivedthe data frames. The amount of memory may be sufficient to storerelatively large amounts of data sufficient to facilitate systems andmethods of performing seismic exploration using an optical link. In someembodiments, the micro-processor 1012 is further configured to send datato the second MAC 1010 when the Link Status and Control module 1016determines that both receivers are receiving valid data.

In some embodiments, the FPGA 1006 includes a buffer 1014 that isaccessible to the micro-processor 1012. The buffer 1014 may includememory that is used by the micro-processor 1012 to save data framesuntil the second MAC 1010 is ready to transmit the data frames.

In some embodiments, the FPGA 1006 includes a receive data sync module1018. The receive data sync module 1018 can build data frames from thedata received from a decoder 1020 (e.g., a 8 B/10 B decoder) and alsoprovide synchronization information to the Link Status and Control block1016. The frames are built by receiving data until an interframe gap isdetected. When the interframe gap is detected, the frame is sent to thesecond MAC 1010 (e.g., at a rate of 1 Gbps). The interframe gap caninclude specific control characters transmitted by the second opticallink 1003 and decoded by the decoder 1020. These control characters caninclude optical signal strength information reported by the secondoptical link 1003. In some embodiments, synchronization data reported tothe Link Status and Control block 1016 can indicate, for example: (1) areceiver is not currently synchronized to the incoming data stream orthere is no data stream; (2) a receiver is synchronized to the incomingdata stream, but the information in that data stream in the form ofcontrol characters indicates that the other side's receiver is notsynchronized to our transmitter; or (3) a receiver is synchronized tothe incoming data stream, and the information in that data stream in theform of control characters indicates that the other side's receiver isalso synchronized to our transmitter.

In some embodiments, the optical link 1001 or FPGA 1006 can include adecoder 1020, such as an 8 B/10 B decoder. The decoder 1020 can receivedata from a de-serializer 1022 and converts the data into 8 bit datacharacters of 8 bit control characters using the 8 B/10 B encodingscheme. The decoder 1020 can synchronize to the data stream upon commandusing control characters in the data stream. In some embodiments, thedecoder 1020 can be configured to decode data using other decodingtechniques that facilitate performing seismic exploration using anoptical link in an aqueous environment.

In some embodiments, the optical link 1001 or FPGA 1006 can include ade-serializer 1022. The de-serializer can receive a serial data streamand produce data (e.g., 10 bit parallel data) suitable for use by thedecoder 1020. In some embodiments, the de-serializer 1022 determines theedges of the received data pulses and adjusts a clock to latch the dataat a suitable point in the data waveform, which may correspond to thecenter of an eye pattern. In some embodiments, when the receive datasynchronizer 1018 sends a synchronize command, the de-serializer 1022can attempt to synchronize with an input data stream using controlcharacters of the synchronization process. The synchronization processmay be is repeated responsive to a command from the receive datasynchronizer 1018.

In some embodiments, the optical link 1001 includes a photo multipliertube (PMT) 1024. The PMT 1024 can be communicatively coupled to the FPGA1006, while being external to the FPGA. The PMT 1024 can includeassociated circuitry that converts incident or received light toelectrical signals suitable for amplification. In some embodiments, thePMT 1024 can include or be communicatively coupled to the opticalreceivers 200 of FIG. 2. In some embodiments, the PMT 1024 can includeor be communicatively coupled to the multi-anode PMT 410 of FIG. 4.

In some embodiments, the optical link includes a gain control 1026. Thegain control 1026 can include a circuit or other hardware that adjuststhe gain of the PMT so that a suitable electrical signal can be producedfrom the incident light. In some embodiments, the gain can be adjustedbased on anode current measured from the PMT and the magnitude of thedata waveform on the signal chain. The gain can be adjusted byincreasing or decreasing the bias voltage on the tube. The gain requiredto get the desired signal is also sent to the link status and controlblock 1016. The gain may also be sent to a transmit/sync generator block1034, which may send the information to the second optical link 1003using control characters in the interframe gap. The second optical link1003 can adjust transmit power based on this information to maintain areliable link over a wide range of optical conditions.

The first and second optical links 1001 and 1003 can include one or morelasers 1030 and 1032 (e.g., optical transmitters 100 of FIG. 2),respectively, that produce an amplitude modulated optical signalcontaining digital information. For example, the laser 1032 can producean optical signal containing digital information received fromserializer 1038. The optical signal can be modulated by modulating thecurrent through the laser 1030 and 1032. The magnitude of thediscrimination current, and therefore the light discrimination, can beadjusted via commands from the link and status control module 1016. Forexample, the magnitude and discrimination can be adjusted to compensatefor optical conditions (e.g., murkiness, turbidity, or murkiness of theaqueous medium).

In some embodiments, the optical link 1001 or FPGA 1006 can include aserializer 1038. The serializer 1038 can receive data (e.g., paralleldata) from an encoder 1036 (e.g., 8 B/10 B encoder) and send a datastream (e.g., serial data stream) to the laser 1032.

In some embodiments, the optical link 1001 or FPGA 1006 includes anencoder 1036. In some embodiments, the encoder 1036 may include an 8B/10 B encoder that converts an 8 bit data stream to a DC balanced 10bit data stream. The data can be any of 256 possible 8 bit data valuesor one of 16 control characters.

In some embodiments, the first optical link 1001 or FPGA 1006 includes atransmit sync generator 1034. The transmit sync generator 1034 canreceive data (e.g., at a data rate of 1 Gpbs) from the second MAC 1010.The transmit sync generator 1034 can buffer the data using a first infirst out memory, and send the data out at a second data rate (e.g., 300Mbps) to the encoder 1036. The transmit sync generator 1034 can send asignal to the microprocessor 1012 indicating that the transmit syncgenerator 1034 is ready to receive more data from the second MAC 1010.The transmit sync generator 1034 can facilitate synchronization by thesecond optical link 1003 by sending synchronization data. The transmitsync generator 1034 can receive a command from the link status andcontrol module 1016 indicating to send the synchronization data to thesecond optical link 1003. In some embodiments, the transmit syncgenerator 1034 can send, to the second optical link 1003, receivedsignal strength information in the inter-frame gaps so that the secondoptical link 1003 can adjust its laser light discrimination.

In some embodiments, the first optical link 1001 or FPGA 1006 includes alink status and control module 1016 that monitors the link status,directs adjustments to transmitter power, or initiates synchronization.For example, the link status and control module 1016 can determine whenthe transmitter should send sync characters based on the sync statusreceived from the second optical link 1003. If the second optical link1003 reports that it is not synchronized or no signal is received fromthe other side, the link status and control module 1016 can facilitatesending synchronization characters. In some embodiments, the link statusand control module 1016 can determines the signal strength informationthe transmitter will send to the other side based on the required PMTgain. In some embodiments, the link status and control module 1016 canset the laser discrimination level based on signal strength informationreceived from the second optical link 1003. In some embodiments, thelink status and control module 1016 can provide link state informationto the micro-processor 1012. The micro-processor 1012 may then providethe link state information it upon request to a host device.

FIG. 11 illustrates an embodiment of a method 1100 of performing seismicexploration in an aqueous medium. The method 1100 can be performed byone or more systems or components illustrated in FIGS. 2-10 in theenvironment illustrated in FIG. 11. For example, the method 1100 can beperformed using FPGA 1006 of FIG. 10 and transceivers 10 and 20 of FIG.2.

In some embodiments, the method 1100 includes receiving sub-aqueousenvironmental data of a first ocean bottom seismometer (OBS) unit (e.g.,a sensor device 30 of FIG. 1) disposed in the aqueous medium (1105).Sub-aqueous environmental data may include, for example, one or more ofseismic data, underwater creature data, turbidity data, water qualitydata, water current data, water opacity data, water temperature data,etc. The OBS unit may receive the sub-aqueous environmental data usingone or more sensors disposed within the OBS unit or one or more sensorsexternal to the OBS. The one or more sensors may include, for example, ageophone, an accelerometer, a gyroscope, a scale, etc. In someembodiments, the OBS unit may be placed at or near an ocean floor orseabed. In some embodiments, the OBS unit may be in contact with, placedon, partially buried or otherwise coupled to the ocean floor. In someembodiments, the OBS unit may be coupled to the seabed via a spike,while in other embodiments the OBS unit may be placed on the ocean floor(e.g., the OBS unit may include a disk-shaped case where a bottomsurface is substantially flat and configured to sufficiently couple withthe ground or seabed such that a geophone disposed within the OBS unitcan receive seismic data).

In some embodiments, the sub-aqueous environmental data includes dataindicating at least one of seismic activity, dissolved solids in theaqueous medium, dissolved minerals in the aqueous medium, a state of theaqueous medium, oxygen concentration in the aqueous medium, saltconcentration in the aqueous medium, plankton concentration in theaqueous medium, turbidity of the aqueous medium, and animal presence inthe aqueous medium. The OBS unit may include (internally or externally)or have access to one or more sensors configured to receive, identify,determine or otherwise obtain the sub-aqueous environmental data.

In some embodiments, the method 1100 includes converting the sub-aqueousenvironmental data into an optical signal (1110). The optical signal canbe formatted for optical transmission in the aqueous medium. Forexample, a data conversion module of the OBS unit can convert thesub-aqueous environmental data received by the OBS unit into a firstformat having one or more channel coding techniques. The channel codingtechniques may include, for example, on-off keyed format, 8 b/10 bencoding, pulse-position discrimination, Quadrature Phase Shift Keying(QPSK), and Quadrature Amplitude Discrimination. In some embodiments,the first format can include or be associated with one or moreparameters such as a frequency, data rate, wavelength, angle, bandwidth,intensity, photon density, etc. For example, the method 1100 may includeusing one or more components of system 1000 such as a microprocessor1012, MAC 1010, transmit/sync generator 1034, encoder 1036 or serializer1038 to convert or transmit the sub-aqueous environmental data into anoptical signal.

In some embodiments, the method 1100 includes transmitting the opticalsignal in the first format through the aqueous medium (1115). Forexample, an optical transmitter of the OBS unit can be configured totransmit the optical signal in the first format through the aqueousmedium. The optical signal can be transmitted based on the first format,one or more parameters, or a channel coding technique. In someembodiments, the method 1100 includes the transmitting the opticalsignal using a light source or other optical transmitter such as a solidstate light source, an InGan based light source, a laser or an LED. Insome embodiments, the optical transmitter may be a component of atransceiver, such as transceiver 10 or 20 illustrated in FIG. 2.

In some embodiments, the method 1100 includes transmitting the opticalsignal using a single-carrier transmission discrimination technique. Insome embodiments, the method 1100 includes transmitting the opticalsignal using a multi-carrier discrimination technique. For example, themulti-carrier discrimination technique may include multiplexingtechniques. In some embodiments, the multi-carrier transmissiontechnique may include an optical Orthogonal Frequency DivisionMultiplexing technique.

In some embodiments, the data rate of the optical signal transmittedthrough the aqueous medium can range from about 10 Mbps to about 300Mbps. In some embodiments, the data rate can range from about 10 Mbps toabout 1 Gbps. In some embodiments, for example in certain types ofmonitor unit, lower data rates as low as 10 Mbps or 100 Mbps may beused.

In some embodiments, the method 1100 includes receiving the opticalsignal transmitted through the aqueous medium. For example, an opticalreceiver of at least one of a remotely operated vehicle (ROV),autonomous underwater vehicle (AUV), or autonomously operating vehicle(AOV) can receive the optical signal. The method 1100 may includereceiving the optical signal via optical receivers 200 or transceivers10 or 20 illustrated in FIG. 2 or using PMT 1024 illustrated in FIG. 10.

In some embodiments, the method 1100 may include converting the opticalsignal transmitted through the aqueous medium into a non-optical signalhaving a second format (1125). In some embodiments, the non-opticalsignal may refer to an electrical signal that can be transmitted via awire or cable. In some embodiments, the non-optical signal includes theelectrical signal configured for transmission through a fiber opticalcable or other cable to a marine vessel (e.g., a ship at the surface ofthe ocean).

In some embodiments, the second format of the non-optical signal orelectrical signal transmitted through the aqueous medium is differentthan the first format of the optical signal. For example, the secondformat of the electrical signal may include a data rater that is higherthan a data rate of the first format of the optical signal. The data ofthe second format may be higher because the electrical signal ornon-optical signal is transmitted through a cable, rather than opticallythrough the aqueous medium.

In some embodiments, the method 1100 includes a plurality of OBS unitstransmitting one or more optical signals through the aqueous medium. Forexample, a first OBS unit may transmit an optical signal through theaqueous medium to a second OBS unit. The second OBS unit may receive theoptical signal and transmit another optical signal to a third OBS unitthrough the aqueous medium. In some embodiments, one of the OBS unitsmay transmit an optical signal to an ROV, AUV or AOV or some otheraccess point through the aqueous medium. The ROV, AUV, AOV or otheraccess point may then convert the received optical signal to anon-optical signal, and transmit the non-optical signal via a cable orwire to the marine vessel or other device that facilitates transmittingdata to the surface of the ocean.

In some embodiments, the first OBS unit transmits a first optical signalto a second OBS unit, and the second OBS unit transmits data of thefirst optical signal in addition to data of the second OBS unit to anROV, AUV, AOV or other access point. Thus, the plurality of OBS unitscan aggregate data transmitted via optical signals through the aqueousmedium to facilitate conveying the data to an ROV or other devicecapable of transmitting the data via a non-optical signal and wire tothe surface of the ocean.

In some embodiments, the method 1100 includes determining acharacteristics of the aqueous medium in order to adjust a parameter orcoding technique associated with transmitting the optical signal. Thecharacteristic can include at least one of a turbidity metric, a waterquality, a water current and an opacity. In some embodiments, the methodcan include using the amount of light detected at the receiver tomeasure the amount of light at the receiver and thereby discern thewater clarity (e.g., turbidity) and/or the distance between thetransmitter and receiver. Since the photocurrent at the output of adetector will be approximately equal to the product of the optical powerat the photosensitive element (such as the photocathode), the efficiencyof converting the optical power into photoelectrons (the quantumefficiency) and the gain of the detector, such a measurement can beaccomplished by measuring the output current from the photodetector (thePIN diode, Avalanche Photodiode (APD), Hybrid Photodetector (HPD, vacuumphotodiode, dynode-type photomultiplier or Microchannel-Plate (MCP)-typephotomultiplier, etc.) and also the gain of the photodetector (asmanifested by the bias voltage(s) for the APD, HPD or photomultiplier)and the gain of any amplifier elements.

Another embodiment will use the measurement of the optical power asdescribed in the preceding paragraph to vary the data rate to ensure alow rate of errors and the maximum effective rate of data transfer.Under conditions where the received transmitter power is weak, due toturbidity, distance between the transmitter and receiver, fouling ordebris at the window, etc., the data rate can be reduced so that thenumber of photons per bit is increased, shot noise at the receiver isreduced, and the error rate is thereby reduced. In some embodiments, anoutput intensity of the optical signal can be increased. In someembodiments, a wavelength of the light can be adjusted to improve datarate (e.g., if it is determined that one or more wavelengths of lightare more likely to be absorbed or reflected off of debris in the aqueousmedium).

In some embodiments, the method 1100 includes initiating an optical linkbetween an OBS unit and at least one of the ROV and the AUV. The method1100 can include transmitting a first optical signal from the OBS unitto the at least one of the ROV and the AUV. The ROV or AUV may determine(e.g., via a microprocessor) that a bit error rate of the first signalis satisfactory, it may determine that a bit error rate is too low. Insome embodiments, the ROV or AUV may compare the bit error rate with athreshold set by an administrator of the system. In some embodiments,the method may include performing a bit error rate test using a biterror rate test pattern (e.g., a pseudorandom binary sequence, quasirandom signal source, 3 in 24, 1:7, Min/Max, all ones, all zeros,alternating 0 s and 1 s, 2 in 8, bridgetap, multipat, or T1-DALY and 55OCTET). In some embodiments, the bit error rate threshold may, forexample, range from about 1e-2 to about 1e-8. In some embodiments, thebit error rate threshold may range from about 1e-3 to about 1e-4.

In some embodiments, the method 1100 can include transmitting a secondoptical signal having a second data rate that is greater than the firstrate. The method 1100 may include selecting the second data rate to behigher than the first data rate responsive to determining that the biterror rate of the first signal satisfies the threshold. For example, ifthe bit error rate of the first signal is relatively good (e.g., 1e-4 orlower), then the method 1100 may include selecting a second data ratethat is higher than the first rate. In some embodiments, the method 1100may include selecting a second data rate based on the bit error rate(e.g., if the bit error rate is relatively low, then the second datarate may be a multiple of the first bit error rate such as twice thefirst data rate).

In some embodiments, the method 1100 includes determining that the biterror rate is less than a threshold or otherwise does not satisfy thethreshold (e.g., the bit error rate is too high). In this case, themethod 1100 may include selecting a second data rate that is less thanthe first data rate (e.g., the second data rate may be about 10% toabout 90% of the first data rate).

In some embodiment, an automatic gain control can be used to provide aslow-start function. Automatic gain control can to allow the receiver tofunction in an optimal range of sensitivity over a range of receivedtransmitter powers. A slow-start can protect a photodetector (e.g., anoptical receiver) that has a voltage-dependent gain, such as an APD,HPD, dynode-type photomultiplier or MCP-type photomultiplier. Thesephotodetectors may be damaged by operation at high light levels orgains. Thus, an automatic gain control that starts by default from a lowgain may prevent damage of the photodetector. In some embodiments, theslow-start automatic gain control can be implemented in hardware using atiming circuit. In some embodiments, the slow-start automatic gaincontrol can be implemented in software for greater flexibility if thetransceiver already includes a micro-controller or other processorsystem for other functionality, such as measuring the receivedtransmitter power, varying bit rates, etc.

FIG. 12 is an illustration of a system 1200 for powering an opticalsystem for performing seismic exploration in an aqueous environment. Insome embodiments, system 1200 includes a wake-up sub-system 1225configured to perform a detect process that can consume low energy(e.g., from about 0 watts to about 1 watts) and a validate process. Thesystem 1200 can determine whether a communications link (e.g., anoptical link) has been properly established and is performing correctly(e.g., using quality control parameters such as bit error rate, or otherhandshaking protocols). In some embodiments, the energy consumption maybe on the order of a hundred micro watts. In some embodiments, thesystem 1200 can use little to no energy by drawing energy from theimpinging wave/signal, be it acoustic or optic. For example, the system1200 can be driven by wave energy, light energy, sound energy, orchemical reactions. In some embodiments, the wake-up sub-system 1225 candraw energy from light provided by an ROV, AUV, or AOV or other lightsource. In some embodiments, a specialty, custom made or other separatebattery can power the wake-up sub-system 1225. This separate battery maybe different from the power-sub system 1205. In some embodiments, thewake-up sub-system 1225 can facilitate a zero power startup or very lowpower startup.

In some embodiments, the system 1200 includes a power sub-system. Thepower sub-system can be provide power to one or more component of thesystem 1200 including, for example, the 3 axis sensor 1210, acquisitionsub-system 1215, storage and control sub-system 1220, extractionsub-system 1230 and wake-up sub-system 1225. In some embodiments, thepower sub-system 1205 includes a fuel cell, battery pack, capacitor, orother energy storage device. In some embodiments, the power sub-systemcan be re-chargeable. In some embodiments, the power sub-system 1205 maynot provide power to the wake-up sub-system 1225 (e.g., the powersub-system 1205 may not be coupled to the wake-up sub-system 1225).

In some embodiments, the system 1200 includes a 3 axis sensor 1210. The3 axis sensor can determine, detect or otherwise identify an orientationof the system 1200 or device including the system 1200 (e.g., an OBSunit or other device in an aqueous medium). The 3 axis sensor candetermine identify a change in an orientation, movement of the sensordevice or other parameter associated with an axis or orientation of thesystem 1200. The 3 axis sensor can be communicatively coupled to anacquisition sub-system 1215 and provide data to the acquisitionsub-system 1215.

In some embodiments, the system 1200 includes an acquisition sub-system1215. The acquisition sub-system 1215 can be configured to receive datafrom the 3 axis sensor 1210 and convey that data to the storage andcontrol sub-system or the wake-up sub-system 1225. The acquisitionsub-system can include one or more logic arrays, microprocessor or othercircuitry to acquire and convey data between one or more component ofsystem 1200.

In some embodiments, the system 1200 includes a storage and controlsub-system 1220. The storage and control sub-system 1220 can include oneor more logic arrays, microprocessor or other circuitry to acquire andconvey data between one or more component of system 1200. The storageand control sub-system 1220 can be configured to communicate with thewake-up sub-system 1225 to initiate power to the various componentssystem 1200. In some embodiments, the storage and control sub-system1220 can facilitate monitoring life in the aqueous medium, such as fish,mammals, or other sea creatures.

In some embodiments, the system 1200 includes an extraction sub-system1230 designed and constructed to extract data stored in, for example, inthe storage and control sub-system obtained via another component ofsystem 1200, and transmit the data via a transmitter 1235. In someembodiments, the extraction sub-system 1230 can include one or morelogic array, processor or other circuits. In some embodiments, theextraction sub-system 1230 can convert the data from one format toanother format for transmitting. In some embodiments, the extractionsub-system 1230 can include a power control, storage interface, linkinterface and processor. The link interface may be communicativelycoupled to the transmitter 1235.

In some embodiments, the system 1200 includes a transmitter 1235. Thetransmitter 1235 may transmit data using, e.g., optical signals, radiofrequency signals, or electrical signals via a wire or cable. In someembodiments, the transmitter 1235 may include an Ethernet link or otherinterface to transmit data.

In some embodiments, the system 1200 includes a detector 1240communicatively coupled to the wake-up sub-system 1225. The detector1240 may include a photodetector, acoustic detector, motion detector,proximity detector, magnetic detector, or other sensor that facilitatesproviding an indication to the wake-up sub-system 1225 to wake up orpower on one or more component of system 1200 or another system forperforming seismic exploration.

While various inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

The above-described embodiments can be implemented in any of numerousways. For example, the embodiments may be implemented using hardware,software or a combination thereof. When implemented in software, thesoftware code can be executed on any suitable processor or collection ofprocessors, whether provided in a single computer or distributed amongmultiple computers.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audible format.

Such computers may be interconnected by one or more networks in anysuitable form, including a local area network or a wide area network,such as an enterprise network, and intelligent network (IN) or theInternet. Such networks may be based on any suitable technology and mayoperate according to any suitable protocol and may include wirelessnetworks, wired networks or fiber optic networks.

A computer employed to implement at least a portion of the functionalitydescribed herein may comprise a memory, one or more processing units(also referred to herein simply as “processors”), one or morecommunication interfaces, one or more display units, and one or moreuser input devices. The memory may comprise any computer-readable media,and may store computer instructions (also referred to herein as“processor-executable instructions”) for implementing the variousfunctionalities described herein. The processing unit(s) may be used toexecute the instructions. The communication interface(s) may be coupledto a wired or wireless network, bus, or other communication means andmay therefore allow the computer to transmit communications to and/orreceive communications from other devices. The display unit(s) may beprovided, for example, to allow a user to view various information inconnection with execution of the instructions. The user input device(s)may be provided, for example, to allow the user to make manualadjustments, make selections, enter data or various other information,and/or interact in any of a variety of manners with the processor duringexecution of the instructions.

The various methods or processes outlined herein may be coded assoftware that is executable on one or more processors that employ anyone of a variety of operating systems or platforms. Additionally, suchsoftware may be written using any of a number of suitable programminglanguages and/or programming or scripting tools, and also may becompiled as executable machine language code or intermediate code thatis executed on a framework or virtual machine.

In this respect, various inventive concepts may be embodied as acomputer readable storage medium (or multiple computer readable storagemedia) (e.g., a computer memory, one or more floppy discs, compactdiscs, optical discs, magnetic tapes, flash memories, circuitconfigurations in Field Programmable Gate Arrays or other semiconductordevices, or other non-transitory medium or tangible computer storagemedium) encoded with one or more programs that, when executed on one ormore computers or other processors, perform methods that implement thevarious embodiments of the invention discussed above. The computerreadable medium or media can be transportable, such that the program orprograms stored thereon can be loaded onto one or more differentcomputers or other processors to implement various aspects of thepresent invention as discussed above.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of embodiments as discussedabove. Additionally, it should be appreciated that according to oneaspect, one or more computer programs that when executed perform methodsof the present invention need not reside on a single computer orprocessor, but may be distributed in a modular fashion amongst a numberof different computers or processors to implement various aspects of thepresent invention.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconvey relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

Also, various inventive concepts may be embodied as one or more methods,of which an example has been provided. The acts performed as part of themethod may be ordered in any suitable way. Accordingly, embodiments maybe constructed in which acts are performed in an order different thanillustrated, which may include performing some acts simultaneously, eventhough shown as sequential acts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03

What is claimed is:
 1. A system to perform seismic exploration in anaqueous medium, comprising: an ocean bottom seismometer (OBS) unitdisposed in the aqueous medium to receive sub-aqueous environmentaldata; a data conversion module of the OBS unit to convert thesub-aqueous environmental data into an optical signal with a firstformat configured for optical transmission via the aqueous medium; atleast one of the OBS unit and an underwater vehicle to: establish,between the OBS unit and the underwater vehicle separated from the OBSunit by the aqueous medium, an optical link through the aqueous medium;and determine a condition of the aqueous medium from a measurement of acharacteristic of the optical link; a controller of the OBS unit toadjust a parameter associated with the optical signal based on thecharacteristic of the aqueous medium; an optical transmitter of the OBSunit to transmit, via the optical link, the optical signal to an opticalreceiver of the underwater vehicle, the optical signal comprising thefirst format and the parameter adjusted by the OBS unit based on thecharacteristic of the aqueous medium; the underwater vehicle to: receivethe optical signal transmitted by the optical transmitter of the OBSunit via the optical link through the aqueous medium; convert,responsive to receipt of the optical signal, the optical signal into anon-optical signal comprising a second format; and provide thenon-optical signal in the second format to a retrieval device.
 2. Thesystem of claim 1, comprising: the retrieval device provided on a marinevessel.
 3. The system of claim 1, comprising: a cable, wherein theunderwater vehicle is further configured to provide the non-opticalsignal to the retrieval device.
 4. The system of claim 1, comprising:the optical receiver of the underwater vehicle further configured tosense an angle of the optical transmitter of the OBS unit; and theunderwater vehicle configured to select, based on a signal from theangle sensed by the optical receiver, an anode in a multiple-anodephotomultiplier tube to align an angular field of view of the opticalreceiver with the optical transmitter.
 5. The system of claim 1,comprising: a photodiode of the optical receiver of the underwatervehicle to generate the non-optical signal comprising an electricaloutput based on light received by the optical receiver from the opticaltransmitter of the OBS unit; and an automatic gain control amplifier ofthe underwater vehicle to adjust a level of the electrical output. 6.The system of claim 1, comprising the OBS unit configured to: detect apresence of the underwater vehicle; and enter a power up stateresponsive to the detection to transmit the optical signal.
 7. Thesystem of claim 1, comprising: an optical transmitter of the OBS unit toenter, responsive to detection of a presence of the underwater vehicle,a power up state to transmit the optical signal, wherein the OBS unit isfurther configured to validate, responsive to the power up state, theoptical link prior to transmission of the optical signal.
 8. The systemof claim 1, wherein the optical transmitter is enclosed in a waterproofcontained, and the optical transmitter comprises a solid state lightsource.
 9. The system of claim 1, comprising the OBS unit configured to:dynamically adjust the parameter in response one or more measurements ofthe characteristic of the optical link.
 10. The system of claim 1,wherein the parameter comprises at least one of a data rate of theoptical signal, an output intensity of the optical signal, a wavelengthof the optical signal, and a gain of the optical receiver.
 11. A methodof performing seismic exploration in an aqueous medium, comprising:receiving, by an ocean bottom seismometer (OBS) unit disposed in theaqueous medium, sub-aqueous environmental data; converting, by a dataconversion module of the OBS unit, the sub-aqueous environmental datainto an optical signal having a first format configured for opticaltransmission via the aqueous medium; establishing, between the OBS unitand an underwater vehicle separated from the OBS unit by the aqueousmedium, an optical link through the aqueous medium; determining, by atleast one of the OBS unit and the underwater vehicle, a condition of theaqueous medium by measuring a characteristic of the optical link;adjusting, by the OBS unit, a parameter associated with the opticalsignal based on the characteristic of the aqueous medium; transmitting,by an optical transmitter of the OBS unit via the optical link, theoptical signal to an optical receiver of the underwater vehicle, theoptical signal comprising the first format and the parameter adjusted bythe OBS unit based on the characteristic of the aqueous medium;receiving, by the optical receiver of the underwater vehicle, theoptical signal transmitted by the optical transmitter of the OBS unitvia the optical link through the aqueous medium; converting, by theunderwater vehicle responsive to receiving the optical signal, theoptical signal into a non-optical signal comprising a second format; andproviding, by the underwater vehicle, the non-optical signal in thesecond format to a retrieval device.
 12. The method of claim 11,comprising: providing the retrieval device on a marine vessel.
 13. Themethod of claim 11, comprising: providing, by the underwater vehicle viaa cable, the non-optical signal to the retrieval device.
 14. The methodof claim 11, comprising: sensing, by the optical receiver of theunderwater vehicle, an angle of the optical transmitter of the OBS unit;and selecting, by the underwater vehicle, based on a signal from theangle sensed by the optical receiver, an anode in a multiple-anodephotomultiplier tube to align an angular field of view of the opticalreceiver with the optical transmitter.
 15. The method of claim 11,comprising: generating, by a photodiode of the optical receiver of theunderwater vehicle, the non-optical signal comprising an electricaloutput based on light received by the optical receiver from the opticaltransmitter of the OBS unit; and adjusting, by an automatic gain controlamplifier of the underwater vehicle, a level of the electrical output.16. The method of claim 11, comprising: detecting, by the OBS unit, apresence of the underwater vehicle; and entering, by the opticaltransmitter of the OBS unit, a power up state responsive to thedetection to transmit the optical signal.
 17. The method of claim 11,comprising: detecting, by the OBS unit, a presence of the underwatervehicle; entering, by the optical transmitter of the OBS unit, a powerup state responsive to the detection to transmit the optical signal; andvalidating, responsive to entering the power up state, the optical linkprior to transmitting the optical signal.
 18. The method of claim 11,wherein the optical transmitter is enclosed in a waterproof contained,and the optical transmitter comprises a solid state light source. 19.The method of claim 11, comprising: dynamically adjusting, by the OBSunit, the parameter in response measuring the characteristic of theoptical link.
 20. The method of claim 11, wherein the parametercomprises at least one of a data rate of the optical signal, an outputintensity of the optical signal, a wavelength of the optical signal, anda gain of the optical receiver.